Patent GB-1081723-A (GB)
Title: Vapor growth of crystals
IPC: C30B29/60
Filed: 1965-04-06
Abstract: Crystals of silicon, germanium, silver, are obtained in the form of ribbons or of sheets by heating the particular material, or a readily decomposable compoun thereof, in a crucible 18 so that it vaporizes in a vessel 12 which also contains a seed crystal 24 having the same crystal structure as the material to be crystallized and having at least one internal twin plane an edge of which is exposed at the bottom of a groove formed between pre-selected surfaces of the seed crystal, and maintaining the temperature of the pre-selected surfaces slightly below the condensation temperature of the vapour whereby crystal growth takes place on the pre-selected surfaces.  The crucible 18 and the seed 24 are heated by resistance heating coils 22, 28, respectively.  The seed crystal shown in Fig. 5 has two twin planes 240 and 242.  Twin plane 240, exposed at the intersection of surfaces 260 and 262, appears as a ridge R at the sides and as a groove G at the tip of the seed crystal. Twin plane 242, exposed at the intersection of surfaces 262 and 264, appears as a groove G at the sides of the seed crystal and a ridge R at the tip. Crystal growth is initiated at the exposed edges of the twin planes, and proceeds in an upward and downward direction.  The seed crystal may be mounted on a substrate, and by this means, crystalline semi-conductor material may be grown on a metallic contact member. An apparatus is described Fig. 22 (not shown) wherein vapour of the material to be crystallized flows out of a nozzle on to the tip of the crystal, a shield being provided so that the vapour does not come into contact with the substrate.  A semi-conductor device comprising crystalline silicon-grown on molybdenum may be made in this way.  The silicon may be doped after growth by vapour diffusion, e.g. with boron. The vapour to be condensed may be formed by a chemical reaction, e.g. silicon tetrachloride or germanium tetrachloride may be reduced with hydrogen.  In the case of a substrate which is normally reactive in the growth environment, e.g. molybdenum in an atmosphere of hydrogen chloride, the seed crystal and substrate may be covered with a layer of molten metal such as indium, tin, gold or gallium. The vapour then saturates the layer of molten metal and migrates to the twin planes of the seed crystal.ALSO:<PICT:1081723/C1/1> <PICT:1081723/C1/2> Crystals of silicon, gallium arsenide, indium antimonide, zinc sulphide or selenide or silicon carbide, are obtained in the form of ribbons or of sheets by heating the particular material, or a readily decomposable compound thereof, in a crucible 18 so that it vaporizes in a vessel 12 which also contains a seed crystal 24 having the same crystal structure as the material to be crystallized and having at least one internal twin plane an edge of which is exposed at the bottom of a groove formed between pre-selected surfaces of the seed crystal, and maintaining the temperature of the preselected surfaces slightly below the condensation temperature of the vapour whereby crystal growth takes place on the preselected surfaces.  The crucible 18 and the seed 24 are heated by resistance heating coils 22, 28, respectively.  The seed crystal shown in Fig. 5 has two twin planes 240 and 242.  Twin plane 240, exposed at the intersection of surfaces 260 and 262, appears as a ridge R at the sides and as a groove G at the tip of the seed crystal.  Twin plane 242, exposed at the intersection of surfaces 262 and 264, appears as a groove G at the sides of the seed crystal and a ridge R at the tip.  Crystal growth is initiated at the exposed edges of the twin planes, and proceeds in an upward and downward direction. The seed crystal may be mounted on a substrate, and by this means, crystalline semi-conductor material may be grown on a metallic contact member.  An apparatus is described (Fig. 22-not shown) wherein vapour of the material to be crystallized flows out of a nozzle on to the tip of the crystal, a shield being provided so that the vapour does not come into contact with the substrate. The charge to be vaporized may be (a) the element or compound, e.g. Si or GaS, and a halogen, e.g. I2, which combine and then decompose, (b) the components of a compound, e.g. In and Sb, or (c) a halogen compound which reacts with H2, e.g. SiCl4, SiHCl3, SiI4, or GaCl2 and As.